Preserve hyphens in Cargo.toml renamed deps

Summary:
This will make autocargo-generated Cargo.toml more closely match what is written in BUCK.

For example this dependency:

https://www.internalfb.com/code/fbsource/[857a404e0bb1db91aef446dc6e767768a8cc36e6]/fbcode/eden/mononoke/mercurial/BUCK?lines=6-7%2C9-11%2C13%2C41

should be generated as `futures-old`, not `futures_old`.

https://www.internalfb.com/code/fbsource/[857a404e0bb1db91aef446dc6e767768a8cc36e6]/fbcode/eden/mononoke/mercurial/revlog/Cargo.toml?lines=3-4%2C13%2C20

Reviewed By: michalmuskala

Differential Revision: D115659800

fbshipit-source-id: 98c49748815d96ca8bea02e25b81f46abef4579b

Author: David Tolnay

below/model/Cargo.toml

@@ -18,7 +18,7 @@ cgroupfs = { version = "0.11.0", path = "../cgroupfs" }
 common = { package = "below-common", version = "0.11.0", path = "../common" }
 enum-iterator = "2.3.0"
 ethtool = { package = "below-ethtool", version = "0.11.0", path = "../ethtool" }
-gpu_stats = { package = "below-gpu-stats", version = "0.11.0", path = "../gpu_stats" }
+gpu-stats = { package = "below-gpu-stats", version = "0.11.0", path = "../gpu_stats" }
 hostname = "0.4.2"
 os_info = "3.15.0"
 procfs = { package = "fb_procfs", version = "0.11.0", path = "../procfs" }